1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a light guide plate, a lighting apparatus using the light guide plate, and a method of fabricating the light guide plate, and more particularly, to a light guide plate used in a backlight or a front light that is used as a lighting apparatus for displays.
2. Description of the Related Art
In general, backlight apparatuses illuminate flat panel display apparatuses such as liquid crystal display (LCD) apparatuses, and can be classified into direct type backlight apparatuses and light guide type backlight apparatuses according to a location of a light source. In addition, the light guide type backlight apparatuses are classified into flat type backlights and wedge type backlights.
In direct type backlight apparatuses, a light source is located right under a light-exiting surface so as to perform a surface-emission, and thus, a plurality of light sources can be arranged to improve a brightness and a light emitting surface can be increased. However, power consumption is increased, and it is difficult to diffuse the light sufficiently when the display is thinned. Then, a shape of a lamp in the light source is projected through a display screen, and thus, the uniformity of the brightness is degraded.
A light guide type backlight apparatus has a structure, in which light is incident from an edge of the light guide plate and is discharged through a light-exiting surface of the light guide plate, which is perpendicular to the edge of the light guide plate. Since the light source is disposed on the edge or a side surface of the light guide plate, a lateral length of the light guide plate limits the number of light sources. In addition, although it is easy to make the light guide type backlight apparatus thin, a structure for evenly distributing the brightness throughout the light emitting surface is more complicated than that of the direct type backlight apparatus.
A flat type backlight apparatus is used in monitors or cases requiring a high brightness. Light sources can be fixed on side edges or four corners of the light guide plate. In addition, in order to improve the brightness using a plurality of light sources, a thickness of the light guide plate must be constant.
A wedge type backlight apparatus is used when it is difficult to use a plurality of light sources because the power consumption is restricted, for example, in laptop computers. The wedge type backlight apparatus can be formed to have a structure, in which a surface, to which the light is incident, has a large area and the other surface has a small area, so as to reduce the weight of the wedge type backlight apparatus.
Line sources or point sources can be used as the light sources used in the light guide plate type backlight apparatus. Cold cathode fluorescent lamps (CCFL), in which electrodes are formed on both end portions of a tube, can be used as the line sources, and light emitting diodes (LEDs) can be used as the point sources. CCFL can emit high-intensity white light, obtain the light having high brightness and high uniformity, and can be designed to each have a large area. However, CCFL are driven by radio frequency alternating current (AC) signals, and operate within a small temperature range. LEDs emit light having lower brightness and lower uniformity than that of CCFL, however, LEDs are driven by a direct current (DC) signal within a large temperature range and have a long lifespan. In addition, LEDs may be formed to be thin.
On the other hand, a front light apparatus is located on a front portion of a display, and can be applied to, for example, a flexible display, which is referred to as e-paper. In the front light apparatus applied to the flexible display, the light source is disposed on edges of the light guide plate, and the front light apparatus is installed on the front portion of the flexible display to provide the flexible display with illumination light. The light guide plate used in the front light apparatus must transmit the display light reflected from the flexible display while illuminating the light from the edges to the flexible display, which is located on the rear portion of the front light apparatus. Therefore, the light guide plate used in the front light apparatus must transmit the display light reflected from the display, as well as provide the display with the light from the light source efficiently.